Application of cadmium-zinc-telluride detectors in 235U enrichment measurements☆

Abstract High-resolution, gamma- and X-ray spectrometry are used routinely in nuclear safeguards verification measurements of plutonium and uranium in the field. These measurements are mostly performed with high-purity germanium (HPGe) detectors, that require cooling to liquid-nitrogen temperatures, thus limiting their utility in field and unattended safeguards measurement applications. NaI scintillation detectors do not require cooling, but their moderate energy resolution (10% at 122 keV) is insufficient in most cases for reliable verification measurements. Semiconductor detectors that operate at room temperature, such as cadmium-zinc-telluride (CdZnTe) detectors, with energy resolution performance reaching 2.0% at 122 keV may complement HPGe detectors for certain safeguards verification applications. We used a 5 × 5 × 5 mm CdZnTe detector to measure 235 U enrichments ranging from 3% to 75%. We use a spectrum analysis technique that fits 235 U, 238 U, and U K X-ray response profiles to data in the 89- to 100-keV region of a gamma-ray spectrum. From the relative magnitudes of the 235 U and 238 U profiles we determine the 235 U enrichment with an accuracy of about 10% with CdZnTe detectors.